Rapid discrimination of amino acid drinks using microscopic Fourier-transform infrared spectroscopy and electrospray ionization mass spectrometry

A rapid discrimination method of amino acid drinks (AADs) by microscopic Fourie-transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS) was studied for forensic identification. The ten descriptions of PET bottle AADs (several tens mu L) were used as samples. Types of saccharides contained mainly in the drinks were given by the FT-IR analysis. The results by the ESI-MS analysis of samples diluted twice with acetonitrile were as follows : amino acids and saccharides were mainly detected as [M + H](+) and [M + Na(or K)](+), respectively, in the positive mode. Acidity regulators and saccharides were mainly detected as [M-H](-) and [M + Cl](-), respectively, in the negative mode. The FT-IR and ESI-MS analyses used in this study rapidly discriminated all samples of the AADs, and could be applied to screening tests of the AADs.